Placing fertilizer both shallow and deep, and planting in the middle of the berm, can maximize your strip-till corn yields.
For successful results in strip-till, fertilizer needs to be placed in a zone where the roots and seedlings of corn can readily access plant-food nutrients.
But soil types, weather conditions and soil-sample results that affect the application timing and fertilizer placement and choice can all be major factors in that success.
For example, shallow placement of anhydrous ammonia in spring strip-tilled fields can burn the roots and kill germinating corn. And if strip-tillers apply anhydrous ammonia in the fall when the soil temperature is too warm — or if they strip-till into sandy soils — nitrogen can drop out of the seed zone.
Fertilizer programs and placement need to be just right, leaving an array of important choices for strip-tillers to make.
David Hardy of Fairview, Mont., strip-tills corn and sugar beets under center pivots, which irrigate about 60% of his acres. He also grows malting barley, wheat and alfalfa for a cow-calf operation.
Hardy uses a 270-horsepower John Deere 8270R tractor to pull his 12-row Strip Cat strip-till rig — set to 26-inch spacings — and a 6-ton Montag fertilizer cart.
Before strip-tilling in the fall, Hardy soil tests each field and applies about 85% of the recommended amount of nitrogen. Since phosphorus and potassium don’t move in the soil, Hardy applies 50% of the recommended rates, based on soil-test results.
“We have high-pH soils — 8 to 8.8 pH is typical,” Hardy says. “Applying 100% of the phosphate and potash in the fall is inefficient, because it will tie up in the soil.”
In the fall of 2011, Hardy decided to place some of the nitrogen, phosphorus and potash at shallower depths than the previous fall, rather than placing it all at one depth.
After seeing his corn grow quite rapidly after emergence in the spring of 2011, and suddenly lag before growing again, Hardy thought he placed the fertilizer too deep the previous fall.
Typically, the mole knives on the Strip Cat place nitrogen at the bottom of the seed trench, 6 to 7 inches deep.
“Gravity always wins,” says Hardy, who estimates 60% to 70% of the fertilizer still finds its way to the bottom of the trench.
But in the fall of 2011, Hardy decided to raise the fertilizer-placement tubes behind the mole knives. After doing this, about 30% of the fertilizer was mixed into the soil, about 3 inches below the surface.
Hardy hopes that placing about 30% of the fertilizer in the top 3 inches of the soil, and the rest about 6 to 7 inches deep in the strip, will help his corn avoid the 2-week lag in growth that he saw last spring. He’ll watch the growth of corn this spring to see if the dual placement keeps corn growing steadily.
Fertilize The Root Zone
Four industry experts agree that a major key to making fertility work in strip-till systems it to place fertilizer in the strip at a depth where corn can easily take in the nutrients.
MAKE ADJUSTMENTS. The mole knives that David Hardy of Fairview, Mont., uses on his strip-till-rig placed nitrogen at the bottom of the trench, 6 to 7 inches deep. But before strip-tilling in the fall of 2011, Hardy raised the fertilizer placement tubes, located behind the mole knives on the strip-till rig, hoping that some shallower-placed fertilizer will keep corn growing steadily in the spring.
Most of these experts favor “dual placement,” with some of the nitrogen, phosphate and potash applied in the top 4 inches of the soil, and more placed 8 to 9 inches down.
Jerry Wilhm, senior research manager at Agro-Culture Liquid Fertilizers in St. Johns, Mich., says there’s still a missing link for optimal placement of crop nutrition, despite the number of advancements in strip-till equipment in recent years.
“Application of dry and liquid fertilizers is usually limited to rather deep placement at the bottom of the shank,” Wilhm says. “This is good for nitrogen and possibly potassium, but the best placement for early access of phosphorus, some starter nitrogen, micronutrients and potassium is in the seed zone.”
Research at Agro-Culture’s 420-acre North Central Research Station in Michigan has shown advantages of dual placement in strip-till using a system the company calls Nutri-Till. It places liquid fertilizer both in the seed zone and at the bottom of the shank, 8 inches below the soil surface.
A custom-built Nutri-Till applicator strip-till rig consists of Yetter coulters and hillers, and an anhydrous shank.
“It’s primarily used for UAN liquid, but we have sent anhydrous through it,” Wilhm says.
A tube at the base of each shank places fertilizer deep in the strip. Shallow seed-zone placement of fertilizer occurs via a solid jet stream from a nozzle that sits between the two side coulters, at the rear of each row unit.
The nozzles run about 1 inch below the surface, so when strips are planted, the seed is in contact with the fertilizer. Because two products are being placed, this fertilizer program requires two separate tanks on the strip-till rig.
“In field testing in 2011, we found that with fertilizer applications made in the fall of 2010, the shallow placement of liquid phosphate, potash and micronutrients yielded 9 bushels more corn per acre than with deeper placement,” Wilhm says. “Deep placement yielded an average of 8 bushels more corn vs. no phosphate, potash and micronutrients.
“The corn is reaching and using the deep-placed nutrition, but the shallow placement is better.”
Complement Corn Roots
Gene Carstens, co-owner of Minden, Neb.-based Twin Diamond Industries, says he agrees with the advice that Orthman Mfg.’s agronomist Mike Petersen gives strip-tillers about fertilizer placement.
Both Carstens and Petersen say strip-tillers need to apply fertilizer in the 0-to-4-inch range and additional fertilizer in a deeper zone, about 8 to 9 inches below the soil surface.
“Plant roots don’t seek nutrition,” Petersen says. “They live in the presence of nutrition. Roots are pulled down by gravity and follow the warming of soil.
“If nutrition is in the same areas as the growing roots, they will be fed. But if the roots have to hunt for nutrition, the plant suffers and yields suffer.”
In the first 45 days of corn growth, the roots tend to grow in two triangles, one on top of the other, Petersen says. The corn roots in the top triangle represent the first shallow growth in that triangle, which is 6 inches tall and 13 inches across at the base.
The second stage of root growth is in a triangle that is 8 inches tall and 18 inches wide at the base, Petersen says. The top point of the second triangle starts 3½ inches below the surface of the soil, which is the top of the first triangle of root growth.
Roots in the top triangle represent the first 20 days of corn growth, while those in the bottom triangle are the next 25 days of growth.
“We must provide fertilizer for the plant so it’s healthy up to 45 days after emergence, which is when the corn plant determines yield,” he says. “At 45 days after emergence, the plant sets the number of rows around the cob.
“In the next 20 to 40 days — right up to pollination and shortly afterward — the corn plant sets the number of kernels running the length of the ear.”
Carstens recommends strip-tillers take two soil samples — 0 to 4 inches and 4 to 12 inches deep — to see what the potassium levels are in the soil.
“In soil with a cation-exchange capacity of 15, I typically recommend strip-tillers place 66% of the phosphate and potash 8 to 9 inches deep,” he says. “For nitrogen, I recommend split applications for spring strip-tillers, and then have them sidedress and/or apply nitrogen through the center pivot.”
What’s In The Soil?
But it’s not enough to just think about the depth of fertilizer placement, says Keith Diedrick, Pioneer Hi-Bred’s agronomist for west-central Indiana. Strip-tillers must also factor in the levels of phosphorus and potassium in the soil.
“Corn and other plants struggle for phosphorus and potassium when soil-test levels are very low, and that holds true if these nutrients are banded in a strip or broadcast,” he says. “There’s probably some benefit to shallower placement of nitrogen and phosphorus — 2 to 4 inches deep — where the band of fertilizer would act similarly to a starter band in a 2-by-2-inch placement.”
Diedrick says he’s leery of applying high quantities of nitrogen or potash in-furrow. That creates the risk of stand loss by “salting out,” where seeds can’t take in water effectively.
“Most sources say we generally ought to limit the total pounds of urea-containing nitrogen, plus 0-0-60 potash, in a 2-by-2-inch band to no more than 70 to 100 pounds per acre in corn,” Diedrick says. “But in-furrow with the seed, the limit for nitrogen and potash is a total of 5 to 10 pounds per acre.
“It’s always safer with a 2-by-2-inch band, rather than in-furrow with seed, which is why calibration and settings are so important.”
Research on starter-fertilizer benefits in conventional tillage doesn’t always show a yield advantage, Diedrick says. But when it does, the starter benefit is usually in cooler, wetter springs.
“As a whole, the majority of a strip-tilled field may be slightly cooler than its conventional counterpart and, as result, the response to a starter band of fertilizer may be greater,” he says.
Hit The Bullseye
While strip-tillers focus on placing fertilizer at the proper depth, they also need to plant on target, too.
That means planting into the middle of the berm in the midst of the fertilizer, and not far off to the side of the nutrients. Numerous research studies show reductions in corn yields when kernels are planted away from the fertilizer under the berm, says Petersen.
This includes results from a study the University of Minnesota Extension did in the fall of 2010 and 2011 growing season.
Using RTK at a research site at Morris, Minn., University of Minnesota strip-till specialist Jodi DeJong-Hughes planted corn in the middle of a strip-tilled berm, then 4 inches over from the middle on the berm’s inside edge.
“Three of the four replications showed an average difference of 11 bushels per acre — or a 5.5% increase in yield — with the seed planted in the middle of the berm vs. on the edge,” DeJong-Hughes says. “The difference in yield has to do with temperature and direct placement of seed over the fertilizer band.”
Caution On Sandy Soils
Brandon Bonk, who farms near Dover, Del., strip-tilled for the first time in the spring of 2011 after researching the system for a year.
Bonk strip-tilled 1,260 acres, including all of his corn and about 50 acres of soybeans. He grows about 1,100 acres of full-season and double-cropped soybeans and 600 acres of no-till wheat, and irrigates about 1,000 acres of corn.
Bonk built an eight-row strip-till rig with 30-inch spacings on a Krause toolbar that has a 3-point hitch, along with a Blu-Jet coulter cart that carries two 500-gallon tanks of liquid fertilizer. He applies fertilizer that’s in suspension and uses a CDS John-Blue piston pump with a Rawson hydraulic drive motor.
Bonk applies the suspension fertilizer as he strip-tills, and then comes back to plant corn. His strip-till rig creates a strip about 7 to 8 inches wide and 7 to 11 inches deep. Bonk variable-rate-applied fertilizer 5 to 8 inches deep.
“At that depth, corn can reach the fertilizer within several weeks after planting,” he says. “You don’t want it too deep, where the fertilizer could dissipate down into the soil. If the fertilizer is placed deeper, at 10 or 11 inches, the corn won’t find it when it’s needed — as it’s growing.”
The suspension fertilizer Bonk applies contains 30% clear nitrogen, potash and sulfur.
“Normally, the suspension fertilizer has 50 pounds of nitrogen, 110 pounds of potash and some sulfur,” Bonk says. “That’s 100% of the sulfur that the corn needs, and about 25% of the nitrogen.”
Location Is Everything
Strip-tillers choosing suspension fertilizer like it because they can include a lot of potash, says Dave Wharry, precision agriculture specialist at Hoober Inc., based in Middleton, Del. Suspension fertilizer is a good fit for soil that needs more potash than can be provided in other liquid fertilizer formulations.
“With suspension fertilizer placed 5 to 6 inches down in the strip, it’s readily available to roots where the starter fertilizer leaves off,” Wharry says. “Because the suspension fertilizer is where the roots are, the total nutrient levels can be decreased. If we can decrease the amount of nutrients applied while maintaining crop yields, then we can satisfy the environmental demands placed on the agricultural industry.”
When Bonk plants corn in 30-inch rows with his 16-row Kinze 3650 planter, he applies 40 pounds of nitrogen and 15 to 20 pounds an acre of phosphorus, along with some micronutrients, in a 2-by-2-inch placement.
“By placing starter fertilizer 2 inches down and 2 inches away from the corn, we’re putting it where the corn can get up and growing more quickly than if we had broadcast the fertilizer,” Bonk says. “The plant comes up faster and it’s healthier. There are fewer problems with disease pressure if the weather turns cool and damp.”
At the four- or five-leaf-stage of corn, Bonk sidedresses nitrogen 2 inches deep with a 16-row Blu-Jet coulter-knife cart on 30-inch spacings. He applies liquid nitrogen as needed during the growing season with the center pivots.
The results of Bonk’s strip-till debut are a little unclear. From spring to fall, he tended to the nutrition needs of the corn, but Hurricane Irene slammed through Delaware in September.
“Before Irene, the corn looked like it would yield 220 to 230 bushels per acre,” Bonk says. “We lost a lot of corn in the field because of the hurricane.”
A 50-Bushel Increase
For Plainview, Texas, corn and cotton grower Steve Olson, strip-till not only conserves fertilizer, but also saves money since he started the practice around 3 years ago.
Olson uses a 12-row Orthman 1tRIPr set to 30-inch spacings, pulled by a Deere 8310R with duals.
“We’ve got RTK guidance on the 1tRIPr and on the tractor,” he says. “The name of the game is to get as precise as we can.”
Olson applies nitrogen, phosphate and Black Label, a liquid fertilizer from Crop Production Services (CPS), about 8 inches down into the strip. Black Label contains humic acid, organic acid and phosphate, as well as zinc and other micronutrients.
“These help foster the growth of soil bacteria that is beneficial to the soil,” Olson says. “The bacteria eat the fertilizer and convert it to a form that the plant can use for nutrition.”
For strip-tillers, there’s a direct connection between the depth that fertilizer is placed in the strip and the fertilizer that’s subsequently applied, whether it’s sidedressed, foliar applied or applied through an irrigation system, Petersen says. Proper placement of fertilizer in the strip complements the two growth stages of the corn roots in the first 45 days.
Adjusting Placement: By raising the fertilizer placement tubes behind the mole knives on his strip-till rig, Hardy hopes to mix some of the fertilizer in the top 3 inches of the tilled soil in the strip.
“By having enough fertilizer placed both shallow and deep in the strip, the corn seedling and its roots develop well, setting up the plant for steady growth and excellent yields,” Petersen says. “By coming back with fertilizer after the corn emerges, strip-tillers can build on the ‘fertilizer foundation’ they made in the strip before planting.
“In other words, the depth of placement of the fertilizer in the strip is an essential part of the total fertilizer program for strip-tillers who want to maximize plant health and yields.”
Olson applies 50 to 60 units of nitrogen and 80 to 90 units of phosphate, along with some zinc and sulfur. The fertilizer is carried in two 500-gallon tanks that ride on the Orthman combo caddy over the 1tRIPr.
During the growing season, Olson works with CPS, which has a NutriScription program. A CPS agronomist takes leaf and petiole samples around V9 or V10, and then when the corn is at the milk stage.
“We analyze these tissue samples and create a graph to see where the fertility levels are at,” Olson says. “You can save so much money because you’re only giving the corn the nutrition that it needs.”
If the crop needs nitrogen, Olson puts it on through the center-pivot irrigation system. If the crop needs micronutrients, Olson feeds the corn with a foliar application, using a John Deere 4830 self-propelled sprayer with a 90-foot-wide boom.
If the corn and the cotton are small enough, he can use a coulter rig to precisely place the nitrogen.
“We usually put on foliar fertilizer before the corn tassels, when the corn is around V8 to V10. If we need any micronutrients after that, we normally call in an airplane,” he says. “We usually apply some zinc; for cotton, we apply potassium. Our soil has a lot of potassium, but it’s not so available.”
In the future, Olson says he’d like to place some fertilizer shallow and some of it deep when he strip-tills, because he feels crops would respond better to smaller amounts of fertilizer at different depths.